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1 /*
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2 * Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 #include "incls/_precompiled.incl"
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26 #include "incls/_g1MMUTracker.cpp.incl"
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27
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28 #define _DISABLE_MMU 0
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29
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30 // can't rely on comparing doubles with tolerating a small margin for error
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31 #define SMALL_MARGIN 0.0000001
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32 #define is_double_leq_0(_value) ( (_value) < SMALL_MARGIN )
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33 #define is_double_leq(_val1, _val2) is_double_leq_0((_val1) - (_val2))
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34 #define is_double_geq(_val1, _val2) is_double_leq_0((_val2) - (_val1))
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35
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36 /***** ALL TIMES ARE IN SECS!!!!!!! *****/
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37
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38 G1MMUTracker::G1MMUTracker(double time_slice, double max_gc_time) :
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39 _time_slice(time_slice),
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40 _max_gc_time(max_gc_time),
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41 _conc_overhead_time_sec(0.0) { }
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42
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43 void
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44 G1MMUTracker::update_conc_overhead(double conc_overhead) {
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45 double conc_overhead_time_sec = _time_slice * conc_overhead;
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46 if (conc_overhead_time_sec > 0.9 * _max_gc_time) {
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47 // We are screwed, as we only seem to have <10% of the soft
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48 // real-time goal available for pauses. Let's admit defeat and
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49 // allow something more generous as a pause target.
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50 conc_overhead_time_sec = 0.75 * _max_gc_time;
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51 }
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52
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53 _conc_overhead_time_sec = conc_overhead_time_sec;
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54 }
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55
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56 G1MMUTrackerQueue::G1MMUTrackerQueue(double time_slice, double max_gc_time) :
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57 G1MMUTracker(time_slice, max_gc_time),
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58 _head_index(0),
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59 _tail_index(trim_index(_head_index+1)),
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60 _no_entries(0) { }
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61
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62 void G1MMUTrackerQueue::remove_expired_entries(double current_time) {
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63 double limit = current_time - _time_slice;
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64 while (_no_entries > 0) {
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65 if (is_double_geq(limit, _array[_tail_index].end_time())) {
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66 _tail_index = trim_index(_tail_index + 1);
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67 --_no_entries;
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68 } else
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69 return;
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70 }
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71 guarantee(_no_entries == 0, "should have no entries in the array");
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72 }
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73
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74 double G1MMUTrackerQueue::calculate_gc_time(double current_time) {
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75 double gc_time = 0.0;
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76 double limit = current_time - _time_slice;
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77 for (int i = 0; i < _no_entries; ++i) {
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78 int index = trim_index(_tail_index + i);
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79 G1MMUTrackerQueueElem *elem = &_array[index];
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80 if (elem->end_time() > limit) {
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81 if (elem->start_time() > limit)
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82 gc_time += elem->duration();
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83 else
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84 gc_time += elem->end_time() - limit;
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85 }
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86 }
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87 return gc_time;
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88 }
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89
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90 void G1MMUTrackerQueue::add_pause(double start, double end, bool gc_thread) {
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91 double longest_allowed = longest_pause_internal(start);
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92 if (longest_allowed < 0.0)
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93 longest_allowed = 0.0;
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94 double duration = end - start;
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95
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96 remove_expired_entries(end);
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97 if (_no_entries == QueueLength) {
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98 // OK, right now when we fill up we bomb out
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99 // there are a few ways of dealing with this "gracefully"
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100 // increase the array size (:-)
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101 // remove the oldest entry (this might allow more GC time for
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102 // the time slice than what's allowed)
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103 // concolidate the two entries with the minimum gap between them
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104 // (this mighte allow less GC time than what's allowed)
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105 guarantee(0, "array full, currently we can't recover");
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106 }
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107 _head_index = trim_index(_head_index + 1);
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108 ++_no_entries;
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109 _array[_head_index] = G1MMUTrackerQueueElem(start, end);
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110 }
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111
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112 // basically the _internal call does not remove expired entries
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113 // this is for trying things out in the future and a couple
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114 // of other places (debugging)
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115
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116 double G1MMUTrackerQueue::longest_pause(double current_time) {
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117 if (_DISABLE_MMU)
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118 return _max_gc_time;
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119
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120 MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag);
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121 remove_expired_entries(current_time);
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122
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123 return longest_pause_internal(current_time);
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124 }
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125
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126 double G1MMUTrackerQueue::longest_pause_internal(double current_time) {
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127 double target_time = _max_gc_time;
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128
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129 while( 1 ) {
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130 double gc_time =
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131 calculate_gc_time(current_time + target_time) + _conc_overhead_time_sec;
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132 double diff = target_time + gc_time - _max_gc_time;
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133 if (!is_double_leq_0(diff)) {
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134 target_time -= diff;
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135 if (is_double_leq_0(target_time)) {
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136 target_time = -1.0;
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137 break;
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138 }
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139 } else {
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140 break;
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141 }
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142 }
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143
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144 return target_time;
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145 }
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146
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147 // basically the _internal call does not remove expired entries
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148 // this is for trying things out in the future and a couple
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149 // of other places (debugging)
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150
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151 double G1MMUTrackerQueue::when_sec(double current_time, double pause_time) {
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152 if (_DISABLE_MMU)
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153 return 0.0;
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154
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155 MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag);
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156 remove_expired_entries(current_time);
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157
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158 return when_internal(current_time, pause_time);
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159 }
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160
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161 double G1MMUTrackerQueue::when_internal(double current_time,
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162 double pause_time) {
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163 // if the pause is over the maximum, just assume that it's the maximum
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164 double adjusted_pause_time =
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165 (pause_time > max_gc_time()) ? max_gc_time() : pause_time;
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166 double earliest_end = current_time + adjusted_pause_time;
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167 double limit = earliest_end - _time_slice;
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168 double gc_time = calculate_gc_time(earliest_end);
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169 double diff = gc_time + adjusted_pause_time - max_gc_time();
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170 if (is_double_leq_0(diff))
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171 return 0.0;
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172
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173 int index = _tail_index;
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174 while ( 1 ) {
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175 G1MMUTrackerQueueElem *elem = &_array[index];
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176 if (elem->end_time() > limit) {
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177 if (elem->start_time() > limit)
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178 diff -= elem->duration();
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179 else
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180 diff -= elem->end_time() - limit;
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181 if (is_double_leq_0(diff))
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182 return elem->end_time() + diff + _time_slice - adjusted_pause_time - current_time;
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183 }
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184 index = trim_index(index+1);
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185 guarantee(index != trim_index(_head_index + 1), "should not go past head");
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186 }
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187 }
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